The objectives of this research are a) the development of accurate, rapid and highly sensitive methods of trace element detection in biological samples, and b) the application of these methods to environmental medicine and clinically important human disease. The technique to be used is an extension of classical X-ray fluorescence methodology, differing from the latter in the employment of Van de Graaff accelerated ions rather than X-rays for the generation of the X- ray spectra. Different methods of sample preparation will be evaluated with a view to simplifying and optimizing the results. A major goal will be the improvement in sensitivity through the use of chemically clean and ultra thin substrate films. Emphasis will be placed on multi- element analysis of single specimens. The determination of the sensitivity, reproducibility and precision of the method will be made for all elements studied and compared with other analytic methods. Normal values of trace element concentrations in blood, urine and tissues will be determined. Samples from patients with diseases including cancer, kidney disease, liver disease, and a variety of metabolic diseases will be studied. The method is capable of detecting all elements with atomic number greater than 15. Preliminary experiments suggest that a sensitivity of 1 to 10 picograms will be achievable.